1. Field of the Invention
This invention relates to a safety manometer which has a protective front window shield that remains in place even when subjected to super atmospheric pressure released inside the manometer behind the window shield.
According to DIN [German Industrial Standard] standards (DIN No. 16,006, Part 1, October, 1976) safety manometers must have a rupture-resistant partition arranged between the dial and the elastic measuring member. It is further required that the holding ring for the window shield is formed and fastened to the casing in such a way that the window shield and the connection to the casing are not released upon release of super-atmospheric pressure inside the manometer. In addition, the back face of the casing must be constructed in such a manner that a discharge opening of at least 90% of the back face is made free upon subjection of the interior of the manometer to superatomospheric pressure.
2. Description of the Prior Art
A safety manometer of the aforementioned type which meets these demands has been known from DOS [German Unexamined Laid-Open Application] No. 2,249,266. In this safety manometer the partition is fixedly attached in the cylindrical casing with tongues by welding, rivets, or the like. On its front face the casing bears a bayonet ring, which is connected to it with the aid of a bayonet catch. Located in the beaded, free end of this bayonet ring is an elastic holding ring which tightly receives the window shield.
When this prior known manometer is assembled, first the partition is welded into the casing with the aid of the tongues. Then the support with the measuring member and with the indicator mechanism but without the dial and without the pointer is inserted through the rear opening of the casing and in so doing the support extension is pushed outward through the casing hole. During this process the indicator shaft and a connecting piece, coaxial to said indicator shaft and fastened on the support, are passed through a hole in the partition. The dial is subsequently placed into the housing through the front opening of the casing and said dial is fastened on the connecting piece, whereupon the pointer is positioned on the indicator shaft. Finally the bayonet ring with the window shield is fastened to the front face of the casing and the back face is inserted into the rear opening of the casing.
The manufacture and assembly of the conventional safety manometer are expensive and elaborate. The welding or riveting of the partition tongues onto the casing leaves traces on the outside of the housing and a subsequent treatment of the housing is necessary to remove these traces. The manufacture of the bayonet catch piece on the front face of the casing and of the bayonet ring is likewise elaborate. Finally, the assembly of the manometer is time-consuming because the dial, which is to be placed in front of the partition, and the pointer can only be mounted after the unit has been incorporated into the housing, and cannot simply be assembled during the manufacture of this unit, consisting of support, measuring member, and indicator mechanism. In this connection, the necessary adjustment of the dial and pointer is extremely tedious.